From e03862c34a31ad716d56cc90cd67446125d614e9 Mon Sep 17 00:00:00 2001
From: Hiroki Shirokura <slank.dev@gmail.com>
Date: Tue, 7 Sep 2021 03:55:01 +0000
Subject: [PATCH] topotests: to create pid file of topotest router

Create a pid file for the router created by topotest.
By executing nsenter directly against this pid, developers
can execute commands directly from outside the unet shell.
This allows the developer to use script, tab completion, etc.,
and improves efficiency.

Signed-off-by: Hiroki Shirokura <slank.dev@gmail.com>
---
 doc/developer/topotests.rst    | 26 ++++++++++++++++++++++++++
 tests/topotests/lib/topogen.py |  4 ++++
 2 files changed, 30 insertions(+)

diff --git a/doc/developer/topotests.rst b/doc/developer/topotests.rst
index 4a8f7bd27d..14da25768f 100644
--- a/doc/developer/topotests.rst
+++ b/doc/developer/topotests.rst
@@ -953,6 +953,32 @@ configuration files (per-daemon) using the following commands:
    end
    r1#
 
+You can also login to the node specified by nsenter using bash, etc.
+A pid file for each node will be created in the relevant test dir.
+You can run scripts inside the node, or use vtysh's <tab> or <?> feature.
+
+.. code:: shell
+
+  [unet shell]
+  # cd tests/topotests/srv6_locator
+  # ./test_srv6_locator.py --topology-only
+  unet> r1 sh segment-routing srv6 locator
+  Locator:
+  Name                 ID      Prefix                   Status
+  -------------------- ------- ------------------------ -------
+  loc1                       1 2001:db8:1:1::/64        Up
+  loc2                       2 2001:db8:2:2::/64        Up
+
+  [Another shell]
+  # nsenter -a -t $(cat /tmp/topotests/srv6_locator.test_srv6_locator/r1.pid) bash --norc
+  # vtysh
+  r1# r1 sh segment-routing srv6 locator
+  Locator:
+  Name                 ID      Prefix                   Status
+  -------------------- ------- ------------------------ -------
+  loc1                       1 2001:db8:1:1::/64        Up
+  loc2                       2 2001:db8:2:2::/64        Up
+
 Writing Tests
 """""""""""""
 
diff --git a/tests/topotests/lib/topogen.py b/tests/topotests/lib/topogen.py
index 325f65dd6f..a76ceaf16b 100644
--- a/tests/topotests/lib/topogen.py
+++ b/tests/topotests/lib/topogen.py
@@ -771,6 +771,10 @@ class TopoRouter(TopoGear):
         # Mount gear log directory on a common path
         self.net.bind_mount(self.gearlogdir, "/tmp/gearlogdir")
 
+        # Ensure pid file
+        with open(os.path.join(self.logdir, self.name + ".pid"), "w") as f:
+            f.write(str(tgen.net.hosts[self.name].pid))
+
     def __str__(self):
         gear = super(TopoRouter, self).__str__()
         gear += " TopoRouter<>"
-- 
2.39.5